Conventionally, there is an intercom system for an apartment complex which is configured by a plurality of residential buildings and a centralized building. In an intercom system disclosed in Patent Literature 1, for example, a building controller which is connected to residential buildings, and which is disposed in a centralized building has a centralized system configuration that centrally manages call signals and the like transmitted from the residential buildings. In the configuration, when the number of residential buildings is increased, the processing power of the controller must be enhanced in accordance with the increasing number, and the cost is raised. Therefore, there is a distributed intercom system in which functions of a building controller of a centralized building that manages call signals are distributed among building controllers of residential buildings, a collective entrance device, a management room master device, and the like.